Electrolytic process and apparatus for making copper dust



Dec. 25, 1951 N. coRslNl ELECTROLYTIC PROCESS AND APPARATUS FOR MAKING COPPER DUST Filed July 28, 1947 OOGOG-GO R m m .z V m J i r Y; lov o o o o mm L, o o oo a Z f o o o o m e o o o o m W ,..I .w o Q o o o o o o` ATTORNEY Patented Dec. 25. 1951 .ELECTROLYTIC PROCESS AND APPARATUS FOR MAKING COPPER DUST Neri Corsini, Firenze,`.ltaly Application July 28, 1947., Serial No. 764,213 In Italy J une 8, 1945 `Section 1, Public Law 690, August v8,1946

Patent expires June 8, 1965 3 Claims.

This invention relates to an electrolytic process and apparatus for making copper dust o1' powder.

.More particularly the invention relates to a method and apparatus for producing Acopper dust that is especially suitable for .the making of copper sulphate.

It is a primary object of this invention, there- `fore. to `provide a `process of electrolytically producing readily oxidiz-able copper dust or powder.

Specifically the invention has for an object to fprovide an electrolytic process of .producing ccpper dust in which the rate of anodic dissolution :is regulated to be substantially equal to the rate :of cathodic deposition.

A stillmore specific object is to provide an electrolytic process of producing copper dust includying `the step of interposing a perforated lead plate anode between a copper anodeand a cathode to maintain the concentration of cupric ions .into carbonate and then into sulphate by treatment with sulphuric acid. In such arrangements `the cathode spacemust be protected with `dia- .phragms However, with my invention Yapplied to theproduction of copper sulphate a simplified industrial process of preparing the same comprises, cathodically depositing copper in the form of a very tine, readily oxidizable dust vas set forth hereinafter, oxidizing the dust at about 500 C. to about 600 Grand dissolving the copper oxide so formed in sulphuric acid.

The method and apparatus for electrolytically producing the readily oxidizable copper dust or powder will be more particularly described as follows:

Employing a cathodio current density range of about 600 to about 800 amps. per sq. m., and electrolyzing an electrolyte containing free sulphuric acid and Cu++ at a low concentration, a very ne metallic dust is deposited on the cathode and precipitates to the bottom of the electrolytic cell utilized. To render this process continuous it is necessary that-the anodeconstitute metallic copper, in practice copper -scrap is `utilized, which copper lanode attacked by the 4acid dissolves to form Cu++ ions.

There is, however, -one diiiiculty, lin that the yield of anodiccurrent is practically quantitative while the cathodic is notably lower. There is therefore a continuous increase in the `quantity of copper dissolved in the electrolyte so `that when a certain limit is reached which limit is dependent-on all the conditions of electrolysis, the copper is no longer deposited at the cathode in the form of a fine dust, but as a compact deposit. Toovercome this disadvantage, a cell is employed in which the soluble copper anode, in practice copper scraps, is largely screened from the cathode by `a lead plate `having a certainnumber of perforations provided therein. This lead plate functions as an insoluble lanode and has .the effect of decreasing .the rate of anodic dissolution of the copper until vthe rateof dissolution substantially equals the rate vof cathodic deposition of the copper .dust. Thus a practically .unvaried concentration of -Cu++ is maintained in the electrolyte.

The exact regulation is obtained by .increasingor reducing in any suitable manner the nurn- Vber and size of the -perforations in th-e lead anode. For instance, the `holes in the upper part of the lead plate may be made larger than those in the lower part and the level of the electrolyte in the cell .raised orloweredsoas to coveror to uncover them.

One construction of a cell embodying asingle cathode which embodies the Vabove .described features is illustrated in the attached drawing, in which:

Figure .1 is transverse section of the cell,

Figure v2 a `longitudinal section theerof, and

Figure 3 Va diagrammaticperspective view of the same.

The cell-is formedfrom Wood or iron' or other suitable material, and lis lined linside with materialwhichisnot liable to corrosion by acid and is a good conductor of current, for example, lead. The cathode I is Vconstituted by a plate of aluminium or of copper. The anode-space or compartment 2, where the metallic copper anode will be placed, is confined at the sides by the walls of the cell, whilst in front of the cathode I the anode space is screened by a lead plate 3, constituting the insoluble anode, in which are formed holes or perforations 4 which provide free passages between the anode space 2 and the cathode l. These holes are more numerous and larger on the upper part ofthe plate. Therefore, by raising or lowering the level of the electrolyte a little so as to cover more or less the larger holes the concentration of Cu++ in the electrolyte can be increased or diminished at will thus keeping the concentration within the desired limits. The metallic dust which separatesgathers in the well or bottom 5 of the cell and is extracted by suitable means. All the cell ,is under a positively. charged tension. Therefore, the copper dust which is deposited on the bottom is also positively charged, however, the amount that is redissolved is negligible.

The Walls of the cell can be lined internally with material that is not subject to corrosion by acid and is non-conductive, such as ebonite, rubber, synthetic resin, stoneware, and the like. However, in these instances the anode compartment 2 must have a lead plate inserted therein on which the metallic copper anode is placed, the inserted plate ensuring electrical contact; V

It is obvious that various types andstructures of anodes and cathodes can be employed in the aforedescribed cell.

It'is thus seen that I have disclosed a method of producing a readily oxidizable copper dust and in embodying this'process in making copper sulphate one proceeds as follows:

Employing a cathodic current density of about 600 to about 800 amps. per Sq. m., an acidity of about 80 to about 120 grams of sulphuric acid per liter and a cupric ion concentration of about to about grams'per liter, the electromotive force -of the cell is of the order of 2 to 2.5 volts. The consumption of energy is of the order of 2 to 2.5 kw.hr. per 1 kg. of dry metallic dust produced.

The metallic dust is by heating it up to about 500 C. to about 600 C. utilizing, for example, an electric oven provided with a temperature reg-` ulator and one that is Well aired. The consumption of energy for this purpose is 0.2 kw.-hr. per 1 kg.' of oxidised dust.

The reaction of the oxide so obtained with sulphuric acid is strongly exothermic. During the reaction in addition to the water and acid required, about one third by volume of the cold saturated solution from the crystallizers should be added. Under these conditions, lthe acidity is very high and the temperature rapidly rises to 100 C. or more, so that the reaction is rapid and complete. The resulting solution is added to the balance of the cold saturated solution in the crystallizers. This permits a smaller solution circulation. y

The method vantages:

(a) The total consumption yof energy is comparatively small, being about 0.6 to about 0.8 kw.hr. per 1 kg. of crystalline copper sulphate produced. Consumption of coal or other fuel is avoided by this method.

(b) The electrolytic cells have no moving parts Vand are not subject to wear; maintenance presents no problem and the operating personnel required is reduced to a minimum.

(c) During the dissolution of the oxide in the acid it is possible to obtain a very high concenproposed Vhas the following ad- 4 tration, thus reducing to a minimum the circulation of the solutions.

(d) The copper sulphate produced is very pure even when produced from scrap copper which contains other-metals as impurities.` It is very easy to recover precious metals remaining in the anodic sludge.

The form of electrolytic cells described may, in addition to being used for making copper sulphate, be used for the electrolytic production o1 metallic copper dust, and other metallic dusts.

l1 claim:

1. The process of preparing a copper dust suitable for conversion to copper sulphate which comprises electrolyzing an electrolyte consisting of free sulfuric acid and cupric ions with a metallic copper anode, the copper being deposited as a fine dust on a cathode, interposng a perforated lead plate anode between the copper anode and the cathode to maintainv the concentration of cupric ions in the electrolyte substantially constant throughout the electrolysis, whereby the rate of anodic dissolution of the copper is regulatedl to be substantially equal to the rate of cathodic deposition of the copper dust, and collecting the precipitated copper dust.

2. The process as claimed in claim 1 wherein the cathodic current density is about 600 to about 800 amperes per square meter, the voltage is 2 to 2.5 volts, and the electrolyte contains about to about grams of sulfuric acid per liter and a cupric ion concentration of about 15 grams per liter. A i

3. A cell for the preparation of a ne copper dust by electrolysis, said cell comprising an anode compartment containing a metallic copper anode, a cathode compartment containing a cathode on which the copper dust is deposited, a well beneath the cathode for the collection of the copper dust, and a perforated lead plate anode positioned between the anode compartment and the cathode compartment.

NERI CORSINI.

REFERENCES CITED UNITED STATES PATENTS Number Name ADate 410,976 Kerner et al. Sept. 10, '1889 881,580 Hess Mar. 10, 1908 890,887 Amenabar June 16, 1908 1,152,772 v Wheeler Sept. 7, 1915 1,777,371 Koehler Oct. 7, 1930 1,804,924 Fitzpatrick et al. May 12, 1931 1,920,819 Rose Aug. 1, 1933 2,228,264 Freedley Jan. 14, 1941 2,326,101 Nichols Aug. '3, 1943 2,356,897 Stack Aug. 29, 1944 FOREIGN PATENTS Number Country Date 11,800 Great Britain Oct. 3, 1885 255,736 Great Britain July 29, 1926 Great Britain Aug. 20, 1931 

1. THE PROCESS OF PREPARING A COPPER DUST SUITABLE FOR CONVERSION TO COPPER SULPHATE WHICH COMPRISES ELECTROLYZING AN ELECTROLYTE CONSISTING OF FREE SULFURIC ACID AND CUPRIC IONS WITH A METAL LIC COPPER ANODE, THE COPPER BEING DEPOSITED AS A FINE DUST ON A CATHODE, INTERPOSING A PERFORATED LEAD PLATE ANODE BETWEEN THE COPPER ANODE AND THE CATHODE TO MAINTAIN THE CONCENTRATION OF CUPRIC IONS IN THE ELECTROLYTE SUBSTANTIALLY CONSTANT THROUGHOUT THE ELECTROLYSIS, WHEREBY THE RATE OF ANODIC DISSOLUTION OF THE COPPER IS REGULATED TO BE SUBSTANTIALLY EQUAL TO THE RATE OF CATHODIC DEPOSITION OF THE COPPER DUST, AND COLLECTING THE PRECIPITATED COPPER DUST. 